Disposable,moisture vapour permeable, liquid impermeable mattress cover having an improved structure for increased stability

ABSTRACT

The present invention relates to a disposable mattress cover which is moisture vapour permeable and liquid impermeable and comprises an improved liquid impermeable formed structure having an enhanced moisture vapour permeability and comprising preferred thermoplastic compositions which can provide a better stability of the mattress cover in use. The disposable mattress cover of the present invention can find a variety of applications wherein moisture vapour permeability combined with liquid imperviousness are desirable, combined with stability in use.

CROSS REFERENCE TO PRIOR APPLICATION

[0001] This is a continuation of International ApplicationPCT/US00/33226, with an international filing date of Dec. 8, 2000, andpublished in English.

FIELD OF THE INVENTION

[0002] The present invention relates to disposable mattress covers whichare moisture vapour permeable and liquid impermeable and compriseimproved liquid impermeable formed structures having an enhancedmoisture vapour permeability and comprising thermoplastic compositionspreferably applied onto a moisture vapour permeable substrate. Themattress covers of the present invention can find a variety ofapplications wherein moisture vapour permeability combined with liquidimperviousness are desirable.

BACKGROUND OF THE INVENTION

[0003] Mattress covers, particularly bed mattress covers, are known inthe art. A primary use of these articles is to protect mattresses,particularly bed mattresses, but also pillows, cushions, duvets,upholstery, from contaminants, e.g. from dust, liquids, or bodilyfluids, for example in environments where a mattress is intended to beused by different users, such as in hospitals, hotels, or rental houses.Known mattress covers are either provided as structures that completelyencase a mattress, or as layers covering the portion of the externalsurface of the mattress that has to be protected, typically at least aportion of the surface of the mattress which is intended, in use, to goin direct or indirect contact with the user, corresponding to the uppersurface in a bed mattress, a cushion or a pillow. Such mattress coversare provided so that a user can use them in order to provide a mattresswith a protective covering, which accordingly can be a partial covering,e.g. substantially limited to an upper surface as explained above, or atotal encasing of the mattress.

[0004] More recently mattress covers have been also proposed to act asan allergen barrier to control house mites that live in the dust,typically on and within mattresses where they can find favourableenvironmental conditions in terms of temperature and nourishment.

[0005] It has long been established that house mites, also known as dustmites, are a source of house dust allergens that not only causeallergies, but also adversely contribute to other pathologies, such asasthma. It has also been established that use of allergen controlmeasures is effective in controlling these conditions. Allergen-proofencasing to contain mites to prevent allergen egress has long been usedin mattresses, such as bed mattresses, pillows, cushions, duvets,upholstery. Mattress covers to be used as allergen barrier against dustmites must therefore completely encase the mattress in order to separatethe user from dust mites and related allergens.

[0006] Mattress covers come in direct or indirect (i.e. through furtherintermediate layers, e.g. bed sheets, or pillowcases) contact with thehuman body, therefore it is important that such covers are moisturevapour permeable for comfort reasons, in addition to being liquidimpermeable in order to provide the mattress with the desired protectionagainst external agents. When used as a barrier against dust mites theymust also have an allergen barrier capability.

[0007] It is also preferred that mattress covers are disposable, thatis, they can be discarded after use with no need of washing orrefurbishing them.

[0008] Various examples of disposable mattress covers which are at thesame time liquid impermeable and breathable, i.e. moisture vapourpermeable, are known in the art, such as for example the bed mattresscovers described in the French patent application FR 2747899.

[0009] Disposable breathable mattress covers known in the art comprisedifferent materials or structures which are capable of providing aliquid barrier, in addition to providing moisture vapour permeability,preferably air permeability, and also having preferred characteristicsin terms of softness, thickness and strength. Such structures ormaterials can comprise a single layer, or multiple layers laminatedtogether. An example are structures comprising thermoplastic microporousfilms, e.g. laminated to fibrous layers such as nonwoven layers.

[0010] Particularly preferred materials which are suitable fordisposable mattress covers are hydrophilic continuous films, also knownas “monolithic films”, that do not allow the flow of moisture vapourthrough open pores or apertures in the material, but do transfersubstantial amounts of moisture vapour through the film by absorbingwater on one side of the film where the moisture vapour concentration ishigher, and desorbing or evaporating it on the opposite side of the filmwhere the moisture vapour concentration is lower.

[0011] In our patent applications EP 98110597.6 entitled “Low viscositythermoplastic compositions for moisture vapour permeable structures andthe utilisation thereof in absorbent articles”, and EP 98110596.8entitled “Low viscosity thermoplastic compositions for structures withenhanced moisture vapour permeability and the utilisation thereof inabsorbent articles”, both applications filed on Jun. 9, 1998,thermoplastic compositions are disclosed for making hydrophiliccontinuous moisture vapour permeable, liquid impermeable layers havingpreferred characteristics of moisture vapour permeability and liquidimperviousness. The disclosed preferred thermoplastic compositions arealso readily processable so as to provide a coating having the desiredthickness onto a substrate, so avoiding the need of complex traditionalextrusion apparatuses. This is achieved by modifying the viscosity ofthe thermoplastic polymers by means of the inclusion in the compositionof a suitable plasticiser or blend of plasticisers that lowers suchviscosity. This allows to utilise with these preferred compositionstypical process conditions known in the art for the direct coating oflow viscosity hot melt compositions onto a substrate in order to form amoisture vapour permeable, liquid impervious film or layer.

[0012] Particularly preferred plasticisers are described in EP98110596.8.

[0013] Disposable, moisture vapour permeable, liquid impermeablemattress covers comprising a moisture vapour permeable, liquidimpermeable structure, which in turn comprises a layer of thethermoplastic compositions according to either EP 98110597.6 or EP98110596.8, preferably applied onto a moisture vapour permeablesubstrate, e.g. a fibrous layer such as a nonwoven layer in order toform a composite structure, are particularly preferred since theyprovide better moisture vapour permeability combined with liquidimperviousness, and also take advantage of the increased ease ofmanufacture associated to the above mentioned compositions. Thesepreferred disposable mattress covers can however be still improved interms of their interaction with a mattress.

[0014] It is in fact preferred that an increased friction is establishedbetween the disposable mattress cover and the mattress surface duringthe use, when i.e. the mattress cover is typically subjected to acertain compression against the mattress itself, in order to minimisepossible misplacements of the cover during its use, for example when themattress is a bed mattress or a pillow, and the mattress cover can bemoved or misplaced by the user's movement, e.g. during the sleep. Thisis particularly important when the mattress cover is intended forpartial covering of the external surface of a mattress, for example ofthe upper surface of a bed mattress, e.g., in combination withtraditional means for connecting the cover to the mattress, such as forexample elastic bands or strands applied at the corners of a rectangularbed mattress cover, according to an embodiment known in the art.

[0015] Provision of an increased friction between the mattress cover andthe mattress is however also useful in the context of a mattress coverintended for total encasing of a mattress. In both cases in fact thisincreased friction prevents or at least reduces relative movementsbetween the mattress cover and the mattress during the use, thereforehelping in keeping the mattress cover in its right position providedinitially, e.g. by the user when applying the cover to the mattress.

[0016] Preferred disposable mattress covers such as those mentionedabove which preferably comprise a layered structure comprising thepreferred thermoplastic compositions according to either EP 98110597.6or EP 98110596.8 applied onto a fibrous substrate, e.g. a nonwoven layersubstrate, typically have the thermoplastic composition whichconstitutes the inner layer of the liquid impermeable, moisture vapourpermeable structure comprised in, or constituting the mattress cover,which inner layer is intended to face the mattress, and therefore tocome in contact with it. Consequently, in the preferred layeredstructure the moisture vapour permeable substrate onto which thethermoplastic composition is applied, typically a fibrous layer, e.g. anonwoven, constitutes the outer layer intended to come in direct orindirect contact with a user, which is also advantageous for comfortreasons.

[0017] It has been surprisingly discovered that by suitably selectingthe components of the preferred thermoplastic compositions comprised inthe liquid impermeable, moisture vapour permeable structure comprised inthe disposable mattress cover of the present invention, it is possibleto confer to the layer formed from the thermoplastic composition acertain tackiness which provides an increased friction towards thematerials of a mattress with which this layer is intended to come incontact in use.

SUMMARY OF THE INVENTION

[0018] A disposable, moisture vapour permeable, liquid impermeablemattress cover comprising a moisture vapour permeable, liquidimpermeable structure. The structure comprises a layer of athermoplastic composition which is intended, in use, to directly contacta mattress.

[0019] The thermoplastic composition comprises:

[0020] from 10% to 80%, preferably from 25% to 70%, by weight of thethermoplastic composition, of a thermoplastic polymer or mixture ofpolymers selected from the group consisting of polyurethanes,poly-ether-amides block copolymers, polyethylene-acrylic acidcopolymers, polyethylene oxide and its copolymers, ethylene acrylicesters copolymers, poly lactide and copolymers, polyamides, polyesterblock copolymers, sulfonated polyesters, poly-ether-ester blockcopolymers, poly-ether-ester-amide block copolymers, polyacrylates,polyacrylic acids and derivatives, ionomers, polyethylene-vinyl acetatewith a vinyl acetate content of more than 28% by weight, polyvinylalcohol and its copolymers, polyvinyl ethers and their copolymers,poly-2-ethyl-oxazoline and derivatives, polyvinyl pyrrolidone and itscopolymers, thermoplastic cellulose derivatives, or mixtures thereof;

[0021] from 20% to 90%, preferably from 30% to 75%, by weight of thethermoplastic composition, of a plasticiser or blend of plasticisersselected from the group consisting of citric acid esters, tartaric acidesters, glycerol and its esters, adipates, sebacates, sorbitol,epoxidized vegetal oils, polymerised vegetal oils, polyols, phthalates,liquid polyesters, glycolates, p-toluene sulfonamide and derivatives,glycols and polyglycols, sorbitan esters, phosphates, monocarboxylicfatty acids (C₈-C₂₂) and their derivatives, and mixtures thereof;

[0022] from 2% to 60%, preferably from 5% to 50%, more preferably from10% to 40%, by weight of the thermoplastic composition, of a tackifierresin or a blend of tackifier resins selected from the group consistingof rosin and rosin esters, terpene-phenolic resins, aromatic resins, andmixtures thereof.

DETAILED DESCRIPTION OF THE INVENTION

[0023] According to the present invention, a disposable, moisture vapourpermeable, liquid impermeable mattress cover is provided which comprisesmoisture vapour permeable, liquid impermeable structures comprising alayer of a highly processable thermoplastic composition having anenhanced moisture vapour permeability and being intended, in use, todirectly contact a mattress. Said layer of said thermoplasticcomposition is capable of providing an increased friction between themattress cover and a mattress in the use conditions.

[0024] The term “mattress”, as used therein, refers to a fabric casefilled with resilient material, such as for example cotton, hair,feathers, foam rubber, or an arrangement of coil springs, and thereforecomprises particularly bed mattresses, but also pillows, cushions,comforters, duvets, upholstered portions of beds (such as headboards),or of sofas or armchairs.

[0025] While in principle the disposable, moisture vapour permeable,liquid impermeable mattress covers of the present invention can becomprised solely of the highly processable thermoplastic compositionscapable of providing the increased friction, it is however preferredthat said thermoplastic compositions are utilised in a compositestructure in combination with one or more other materials to create alayered moisture vapour permeable, liquid impermeable compositestructure comprised in the mattress cover. The composite structure, forexample, can involve two or more components of a same specificthermoplastic composition within the present invention, or differentspecific thermoplastic compositions of the present invention.

[0026] Alternatively, and preferably, the composite structure caninvolve at least one component, typically a layer, of the thermoplasticcomposition in combination with one or more other moisture vapourpermeable materials, provided that the component of the thermoplasticcomposition is intended, in use, to face the mattress and hence to comein direct contact with it. Such moisture vapour permeable materialsinclude, but are not limited to: fibres, fibrous batts, non-wovens,wovens, papers, micro-porous or porous membranes, films such aspolymeric films, perforated or apertured films and papers,macroscopically expanded films, cloth, etc.

[0027] Said other components may be non-absorbent, absorbent,liquid-containing, etc.

[0028] Preferably the composite structures described above have amoisture vapour transfer rate of at least 100 g/m²·24 h, more preferablyat least 300 g/m²·24 h, and most preferably at least 500 g/m²·24 h.

[0029] According to a particularly preferred embodiment of the presentinvention the disposable, moisture vapour permeable, liquid impermeablemattress cover comprises a composite structure comprising a layer of thethermoplastic composition applied onto a moisture vapour permeablesubstrate, wherein said layer is intended, in use, to directly contactthe mattress. The moisture vapour permeable substrate preferablycomprises a fibrous layer, e.g. a nonwoven layer onto which thethermoplastic composition is applied by means of known means, e.g.preferably by hot melt coating.

[0030] A disposable, moisture vapour permeable, liquid impermeablemattress cover comprising a moisture vapour permeable, liquidimpermeable structure in turn comprising a layer of the thermoplasticcomposition according to the present invention which is intended, inuse, to directly contact a mattress, can have any shape and arrangementwhich is known in the art, and which is suitable for its intended use.

[0031] For example, if the mattress consists of a standard bed mattress,the mattress cover can be a substantially rectangular flat sheet withelastic strings at the corners, or alternatively with integrallyelasticised corners, as described in FR 2747899. The rectangular sheettypically has suitable dimensions in order to completely cover at leastthe upper surface of the bed mattress, and preferably, as in the latterembodiment referred to above, also the side surfaces thereof, whereinthe elastic strings or the elasticised corners provide for a suitablereleasable connection, in a way known in the art, to the mattress.Alternative configurations where the mattress cover has a suitable shapeand size in order to completely encase a mattress are also possible.This latter configuration is particularly preferred when the mattresscover, in addition to liquid imperviousness and moisture vapourpermeability, has also to provide a barrier against dust mites andrelated allergens. A closure of the mattress cover providing a tightseal by means of known means, e.g. adhesive means, is also particularlypreferred in this case in order to completely isolate the mattresswithin the mattress cover itself.

[0032] Any other suitable shape or arrangement for a mattress coveraccording to the present invention is also possible, depending on theparticular mattress type, shape and dimensions, and on the intended useof the mattress cover.

[0033] Suitable thermoplastic compositions for forming a layer comprisedin the moisture vapour permeable, liquid impermeable structurescomprised in the disposable mattress covers according to the presentinvention are thermoplastic compositions for making hydrophiliccontinuous moisture vapour permeable, liquid impermeable layers or films(“monolithic films”) having preferred characteristics of moisture vapourpermeability and liquid imperviousness. The thermoplastic compositionsaccording to the present invention comprise preferred thermoplasticpolymers such as polyurethanes, poly-ether-amides block copolymers,polyethylene-acrylic acid copolymers, polyethylene oxide and itscopolymers, ethylene acrylic esters copolymers, poly lactide andcopolymers, polyamides, polyester block copolymers, sulfonatedpolyesters, poly-ether-ester block copolymers, poly-ether-ester-amideblock copolymers, polyacrylates, polyacrylic acids and derivatives,ionomers, polyethylene-vinyl acetate with a vinyl acetate content ofmore than 28 weight %, polyvinyl alcohol and its copolymers, polyvinylethers and their copolymers, poly-2-ethyl-oxazoline and derivatives,polyvinyl pyrrolidone and its copolymers, thermoplastic cellulosederivatives, or mixtures thereof.

[0034] Particularly preferred thermoplastic polymers are thermoplasticpoly-ether-amide block copolymers (e.g. Pebax™), thermoplasticpoly-ether-ester-amide block copolymers, thermoplastic polyester blockcopolymers (e.g. Hytrel™), thermoplastic polyurethanes (e.g. Estane™),or mixtures thereof.

[0035] Such thermoplastic polymers or mixture of polymers can betypically highly viscous in the melted state at the process conditionsthat are typical of the known processes of film or layer formation, e.g.an extrusion process involving a high power screw extruder. For examplethey may have a viscosity higher than 5000 poise at a temperature of 20°C. above the DSC (Differential Scanning Calorimetry) melting point,which is the temperature identified as that corresponding to the DSCpeak, or corresponding to the highest DSC peak in case of a mixture ofpolymers showing more than one peak, and at a frequency of 1 rad/sec.

[0036] The viscosity of the preferred thermoplastic polymers or mixtureof polymers is adjusted by including in the thermoplastic composition asuitable plasticiser, or blend of plasticisers, that is compatible withthe thermoplastic polymers and that lowers the viscosity of thethermoplastic polymer or mixture of polymers in the melted state.

[0037] The thermoplastic compositions according to the present inventioncomprising the suitable plasticiser or blend of plasticisers have thefollowing complex viscosities (η*):

[0038] 50 poise<η*<4000 poise, preferably 100 poise<η*<2000 poise, morepreferably 100 poise<η*<1000 poise, at a frequency of 1 rad/s at atemperature of 210° C. or less and η*<2000 pose, preferably η* <1000poise, more preferably η*<500 poise, at a frequency of 1000 rad/s at aprocess temperature (T) of 210° C. or less, wherein η* represents thecomplex viscosity of the thermoplastic polymeric composition. Preferablythe temperature T is 200° C. or less and more preferably 180° C. or lessand most preferably from 200° C. to 500° C.

[0039] The thermoplastic compositions having the complex viscositydescribed allow for a film or layer to be coated onto a substrate usingtypical coating conditions and apparatuses known in the art for thecoating of low viscosities hot melt compositions in a layer having arequired thickness onto a substrate, while also keeping the advantageouscharacteristics of the preferred thermoplastic polymers in providinghydrophilic continuous moisture vapour permeable, liquid impermeablelayers or films.

[0040] Thermoplastic compositions having such viscosities can alsoprovide very thin films or layers.

[0041] Suitable plasticisers or blend of plasticisers for adjusting suchviscosity can be selected from the group consisting of citric acidesters, tartaric acid esters, glycerol and its esters, adipates,sebacates, sorbitol, epoxidized vegetal oils, polymerised vegetal oils,polyols, phthalates, liquid polyesters, glycolates, p-toluenesulfonamide and derivatives, glycols and polyglycols, sorbitan esters,phosphates, monocarboxylic fatty acids (C₈-C₂₂) and their derivatives,and mixtures thereof. This allows to utilise with these preferredcompositions typical process conditions known in the art for the directcoating of low viscosity hot melts onto a substrate in order to form amoisture vapour permeable, liquid impervious film or layer.

[0042] It has also been found that by further selecting the plasticiseror blend of plasticisers to be comprised in the thermoplasticcomposition according to the present invention from the group ofhydrophilic plasticisers consisting of acids, esters, amides, alcohols,polyalcohols, or mixtures thereof, the advantage of an enhanced moisturevapour permeability of the resulting layer or film formed from thethermoplastic composition is also achieved, when compared to acorresponding film or layer formed from a thermoplastic compositioncomprising the same thermoplastic polymer, but without the plasticiser.

[0043] The preferred hydrophilic plasticiser or blend of hydrophilicplasticisers can of course also adjust the viscosity of thethermoplastic composition according to the present invention to thepreferred values in order to make it processable by coating saidthermoplastic composition onto a substrate in a layer or film having adesired thickness.

[0044] Suitable preferred hydrophilic plasticisers according to thispreferred embodiment of the present invention are citric acid esters,tartaric acid esters, glycerol and its esters, sorbitol, glycolates, andmixtures thereof.

[0045] The thermoplastic compositions comprised in the moisture vapourpermeable, liquid impermeable mattress cover of the present inventionalso comprise a tackifier resin or a blend of tackifier resins.According to the present invention, it has been found that by suitablyselecting the tackifier resin, or blend of tackifier resins, to be addedto the thermoplastic composition, it is possible to adjust the residualtackiness of said thermoplastic composition at room temperature, i.e. inthe solidified thermoplastic composition constituting the layer of themoisture vapour permeable, liquid impermeable structure comprised in themattress cover, which layer is intended to directly contact the mattressin use. This in turn allows an adjustment of the friction that isestablished, in the use conditions, between the layer of saidthermoplastic composition comprised in the disposable mattress cover ofthe present invention, and the mattress surface, when the mattress coveris typically subjected to compression against the mattress itself. Anincreased friction provides in fact a better stability of the liquidimpermeable, moisture vapour permeable mattress cover of the presentinvention with respect to the mattress, avoiding or at least reducingthe relative movements between mattress cover and mattress which can beinduced in use, for example by the user's movements, e.g. during thesleep, when the mattress is a bed mattress or a pillow, and the mattresscover is a bed mattress or a pillow cover. Risk of misplacement of themattress cover during the use is therefore greatly reduced. Moreover,this in turn allows the use of lighter and cheaper materials for thedisposable mattress cover of the present invention, which is beneficialin the context of a disposable mattress cover. Since said materialscomprised in the moisture vapour permeable, liquid impermeable structurecomprised in the mattress cover of the present invention need to resistto a lesser stress during the use, they can be thinner, and thereforeprovide a better moisture vapour permeability in addition to liquidimperviousness, while being also softer and more comfortable for theuser. The disposal of the mattress cover after use also implies a lesserwaste of materials.

[0046] By suitably selecting the tackifier resin or blend of tackifierresins according to the present invention it is also possible to adjustthe residual tackiness at room temperature of the thermoplasticcomposition, and therefore of the layer formed from said thermoplasticcomposition, to the extent that it has the typical characteristics of apressure sensitive adhesive. In other words, the friction between thelayer of thermoplastic composition comprised in the mattress cover ofthe present invention and the mattress can be increased such that themattress cover can actually stick to the mattress, owing to thethermoplastic composition which can be formulated in order to behavelike a pressure sensitive adhesive. Residual tackiness of thethermoplastic composition at room temperature can be suitably tailoredaccording to the present invention since a smooth transition existsbetween increasing friction and actual adhesiveness.

[0047] Preferred tackifier resins, or blend of tackifier resinsaccording to the present invention have a softening point of 125° C. orless, and are selected from the group consisting of rosin and rosinesters, terpene-phenolic resins, aromatic resins, and mixtures thereof.

[0048] More preferably, the thermoplastic compositions according to thepresent invention comprise a blend of tackifier resins, selected asdescribed above, wherein moreover from 0% to 20%, preferably from 2% to15%, by weight of said blend of tackifier resins comprises a resin orblend of resins having a softening point of less than 25° C., and from80% to 100%, preferably from 85% to 98%, by weight of said blend oftackifier resins comprises a resin or blend of resins having a softeningpoint of at least 70° C.

[0049] The presence in the blend of tackifier resins of a certain amountof one or more tackifier resins which are liquid at room temperature ispreferred since said resin or resins, in addition to adjusting theresidual tackiness of the layer formed from the resulting thermoplasticcomposition, also contribute to lower the viscosity of the compositionitself at the process conditions, in combination with the selectedsuitable plasticiser or blend of plasticisers.

[0050] Said preferred blend of tackifier resins therefore provides athermoplastic composition for forming a layer in the moisture vapourpermeable, liquid impermeable structure comprised in the mattress coverof the present invention, which is easily processable. Moreover thepreferred blend of tackifier resins allows to adjust the residualtackiness of the resulting thermoplastic layer made from thethermoplastic composition, and therefore the friction between themattress cover and the mattress in use conditions, which is beneficialas explained above.

[0051] The thermoplastic compositions comprised in the disposable,liquid impervious, moisture vapour permeable mattress covers accordingto the present invention comprise from 10% to 80%, preferably from 25%to 70% by weight of the thermoplastic composition, of the thermoplasticpolymer or mixture of polymers, from 20% to 90%, preferably from 30% to75% by weight of the thermoplastic composition, of a plasticiser orblend of plasticisers, and from 2% to 60%, preferably from 5% to 50%,more preferably from 10% to 40%, by weight of said thermoplasticcomposition, of a tackifier resin or blend of tackifier resins, saidthermoplastic polymers, plasticisers, and tackifier resins selected asdescribed above.

[0052] The thermoplastic compositions according to the present inventionmay in addition comprise additional optional components to furtherimprove the processibility of the compositions and also the mechanicalcharacteristics as well as other characteristics such as resistance toageing by light and oxygen, visual appearance etc., of the films orlayers formed from such thermoplastic compositions.

[0053] Such optional components include anti-oxidants,anti-ultraviolets, pigments and mixtures thereof, which may be presentwithin the composition at a level of up to 10% by weight of thecomposition.

[0054] A thermoplastic composition according to the present inventioncan be manufactured with a process that will typically comprise thesteps of providing the thermoplastic polymer or mixture of polymers, thesuitable plasticiser or blend of plasticisers, and the tackifier resinor blend of tackifier resins, heating the components and compoundingthem, e.g. with a known suitable mixer to form the thermoplasticcomposition in the molten state having the desired complex viscosity η*.

[0055] According to the present invention a moisture vapour permeable,liquid impervious layer can be formed from the thermoplastic compositionof the present invention by coating said thermoplastic composition ontoa substrate. The films or layers formed from the thermoplasticcompositions of the present invention preferably have a moisture vapourtransport rate of at least 100 g/m²·24 h, preferably at least 300g/m²·24 h, most preferably at least 500 g/m²·24 h with a thickness ofthe layer or film of at least 0.5 μm.

[0056] A process for making a layer or film from a thermoplasticcomposition according to the present invention typically comprises thesteps of providing said composition, heating it to make it flowable, andcoating said composition in the molten state onto a substrate in a layerhaving the desired thickness. While said substrate can be simply aformation substrate, onto which the thermoplastic composition is coatedin order to form a film or layer of the desired thickness which issubsequently separated from said substrate and used as such, in apreferred embodiment of the present invention a moisture vapourpermeable, water impervious composite is formed which comprises thethermoplastic composition and a substrate onto which said thermoplasticcomposition is coated, wherein the substrate is also moisture vapourpermeable.

[0057] Such embodiment provides a moisture vapour permeable, liquidimpervious composite structure wherein the contribution of the layerformed from the thermoplastic composition of the present invention tothe performance of the composite material resides only in the provisionof a liquid barrier and hence could be advantageously provided as thinlyas possible. The remaining performance physical criterion beingpreferably provided by the provided substrate, that therefore preferablyacts also as a support layer. Typical thicknesses of the layer of thethermoplastic composition applied onto a suitable substrate to form acomposite structure according to the present invention range from 2 μmto 200 μm.

[0058] The substrate, or support layer may be any useful layer which isalso moisture vapour permeable, preferably having a moisture vapourpermeability of at least 100 g/m²·24 h, more preferably at least 300g/m²·24 h, and most preferably at least 500 g/m²·24 h.

[0059] Suitable substrates for use herein as support layers include twodimensional, planar micro and macro-porous films; macroscopicallyexpanded films; formed apertured films; nonwoven and woven layers.According to the present invention the apertures in said layer may be ofany configuration, but are preferably spherical or oblong and may alsobe of varying dimensions. The apertures preferably are evenlydistributed across the entire surface of the layer, however layershaving only certain regions of the surface having apertures are alsoenvisioned.

[0060] Suitable two dimensional porous planar layers of the backsheetmay be made of any material known in the art, but are preferablymanufactured from commonly available polymeric materials. Suitablematerials are for example Goretex™ or Sympatex™ type materials wellknown in the art for their application in so-called breathable clothing.Other suitable materials include XMP-1001 of Minnesota Mining andManufacturing Company, St. Paul, Minn., USA and Exxaire XBF-101W,supplied by the Exxon Chemical Company. As used herein the term twodimensional planar layer refers to layers having a depth of less than 1mm, preferably less than 0.5 mm, wherein the apertures have an averageuniform diameter along their length and which do not protrude out of theplane of the layer. The apertured materials for use as a backsheet inthe present invention may be produced using any of the methods known inthe art such as described in EPO 293 482 and the references therein. Inaddition the dimensions of the apertures produced by this method may beincreased by applying a force across the plane of the backsheet layer(i.e. stretching the layer).

[0061] Suitable apertured formed films include films which have discreteapertures which extend beyond the horizontal plane of the garment facingsurface of the layer towards the core thereby forming protuberances. Theprotuberances have an orifice located at its terminating end. Preferablysaid protuberances are of a funnel shape, similar to those described inU.S. Pat. No. 3,929,135. The apertures located within the plane and theorifices located at the terminating end of protuberance themselves maybecircular or non circular provided the cross sectional dimension or areaof the orifice at the termination of the protuberance is smaller thanthe cross sectional dimension or area of the aperture located within thegarment facing surface of the layer. Preferably said apertured performedfilms are uni directional such that they have at least substantially, ifnot complete one directional fluid transport towards the core.

[0062] Suitable macroscopically expanded films for use herein includefilms as described in for example in U.S. Pat. No. 4,637,819 and U.S.Pat. No. 4,591,523.

[0063] Preferred support layers for use herein include woven andnonwoven layers, most preferably hydrophobic fibrous layers such ashydrophobic nonwoven.

[0064] The composites of this preferred embodiment according to thepresent invention are particularly advantageous as they allow thepossibility of providing a composite wherein the thermoplasticcomposition may be coated onto the support substrate as a layer with thedesired thickness. Typical coating conditions and apparatuses known inthe art for the direct coating of low viscosities hot melts can bereadily utilised in order to provide the thermoplastic composition atthe desired thickness.

[0065] A possible method for forming a composite laminate by coating thethermoplastic composition onto a substrate acting as a support layer isdescribed in PCT application WO 96/25902.

[0066] At least at the coating temperature, the thermoplasticcomposition in form of a layer preferably exhibits adhesive propertieson the supportive substrate in order to form the preferred compositesuch that no additional adhesive is required to achieve a permanentattachment between the thermoplastic composition and the substrate.

[0067] Preferably the moisture vapour permeable, liquid imperviousstructures, e.g. layers or composites comprising the thermoplasticcompositions according to the present invention, and comprised in themattress covers of the present invention have an overall moisture vapourtransfer rate of at least 100 g/m²·24 h, more preferably at least 300g/m²·24 h, and most preferably at least 500 g/m²·24 h.

[0068] A moisture vapour permeable, liquid impervious compositestructure formed by coating the thermoplastic composition of the presentinvention onto a suitable substrate finds particular utility as astructure constituting a disposable, moisture vapour permeable, liquidimpermeable mattress cover according to the present invention.

EXAMPLE

[0069] A polyether-amide block copolymer available from Elf Atochem(France) commercialised under the trade name Pebax 2533 SN is compoundedwith Tri Butyl Citrate (plasticiser) available from Aldrich Co., Foral85-E (tackifier resin) available from Hercules Company, and Irganox 1010(anti oxidant agent) available from Ciba-Geigy.

[0070] The final formulation in percent by weight has the followingcomposition: 33% Pebax 2533 SN 33% Tri Butyl Citrate 33% Foral 85-E  1%Irganox 1010

[0071] The blend is melt extruded to obtain a film having a thicknessequal to 15 μm. The film is laminated directly onto a substrateconstituted by a carded hydrophobic 100% polypropylene nonwoven 34 g/m²(support layer) commercialised under the trade name Sawabond 4124,available form Sandler (Germany).

[0072] The composite structure is used to produce a mattress cover, e.g.a bed mattress cover having a flat rectangular shape with suitabledimensions to completely cover at least the upper surface of a bedmattress, wherein the layer of thermoplastic composition is intended toface, in use, the mattress, and to directly contact it.

[0073] According to the present invention the complex viscosity η* ismeasured using a Rheometer RDA-II available from Rheometrics Co.Moisture vapour permeability is measured as Water Vapour TransmissionRate (WVTR) at 23° C. according to the ASTM E-96 “Upright Cup” method.The softening point of the resins is measured according to the Ring andBall ASTM E28 method.

What is claimed is:
 1. A disposable moisture vapor permeable and liquidimpermeable mattress cover, said mattress cover comprising a moisturevapor permeable and liquid impermeable structure, said structurecomprising a thermoplastic composition intended for direct contact witha mattress; wherein said thermoplastic composition comprises (a) fromabout 10% to about 80% by weight of said thermoplastic composition, of athermoplastic polymer or a mixture of polymers selected from the groupconsisting of: polyurethanes, poly-ether-amides block copolymers,polyethylene-acrylic acid copolymers, polyethylene oxide, polyethyleneoxide copolymers, ethylene acrylic ester copolymers, poly lactide, polylactide copolymers, polyamides, polyester block copolymers, sulfonatedpolyesters, poly-ether-ester block copolymers, poly-ether-ester-amideblock copolymers, polyacrylates, polyacrylic acids and derivativesthereof, ionomers, polyethylene-vinyl acetate with a vinyl acetatecontent of greater than about 28% by weight, polyvinyl alcohol,polyvinyl alcohol copolymers, polyvinyl ethers, polyvinyl ethercopolymers, poly-2-ethyl-oxazoline and derivatives thereof, polyvinylpyrrolidone, polyvinyl pyrrolidone copolymers, thermoplastic cellulosederivatives and mixtures thereof; (b) from about 20% to about 90% byweight of said thermoplastic composition, of a plasticiser or mixture ofplasticisers selected from the group consisting of: citric acid esters,tartaric acid esters, glycerol, glycerol esters, adipates, sebacates,sorbitol, epoxidized vegetal oils, polymerized vegetal oils, polyols,phthalates, liquid polyesters, glycolates, p-toluene sulfonamide,p-toluene sulfonamide derivatives, glycols, polyglycols, sorbitanesters, phosphates, monocarboxylic fatty acids (C₈-C₂₂), monocarboxylicfatty acid (C₈-C₂₂) derivatives and mixtures thereof; (c) from about 2%to about 60% by weight of said thermoplastic composition, of a tackifierresin or mixture of tackifier resins selected from the group consistingof: rosin, rosin esters, terpene-phenolic resins, aromatic resins andmixtures thereof.
 2. A disposable, moisture vapor permeable and liquidimpermeable mattress cover according to claim 1, wherein saidthermoplastic composition comprises from about 25% to about 70% of saidthermoplastic polymer or mixture of polymers.
 3. A disposable, moisturevapor permeable and liquid impermeable mattress cover according to claim1, wherein said thermoplastic composition comprises from about 30% toabout 75% of said plasticizer or mixture of plasticizers.
 4. Adisposable, moisture vapor permeable and liquid impermeable mattresscover according to claim 1, wherein said thermoplastic compositioncomprises from about 5% to about 50% of said tackifier resin or mixtureof tackifier resins.
 5. A disposable, moisture and vapor permeable andliquid impermeable mattress cover according to claim 1, wherein saidlayer of thermoplastic composition is applied onto a substrate, saidsubstrate being moisture and vapor impermeable.
 6. A disposable,moisture and vapor permeable and liquid impermeable mattress coveraccording to claim 1, wherein said blend of tackifier resins comprisesfrom about 0% to about 20% by weight of said blend of tackifier resins,of a resin or blend of resins having a softening point of less thanabout 25° C., and from about 80% to about 100%, by weight of said blendof tackifier resins, of a resin or blend of resins having a softeningpoint of at least about 70° C., said softening points measured accordingto the Ring and Ball ASTM E28 method.
 7. A disposable, moisture andvapor permeable and liquid impermeable mattress cover according to claim1, wherein said blend of tackifier resins comprises from about 2% toabout 15% by weight of said blend of tackifier resins, of a resin orblend of resins having a softening point of less than about 25° C., andfrom about 85% to about 98%, by weight of said blend of tackifierresins, of a resin or blend of resins having a softening point of atleast about 70° C., said softening points measured according to the Ringand Ball ASTM E28 method.
 8. A disposable, moisture and vapor permeableand liquid impermeable mattress cover according to claim 1, wherein saidlayer of said thermoplastic composition is liquid impervious and has awater vapor transmission rate (WVTR) of at least about 300 g/m²·24 hwith a thickness of said layer of at least about 0.5 μm.